Regulation of Ethanol on Ferrous Oxalate Particle Size and Properties: Theoretical and Experimental Study

Surfactants containing hydroxyl functional groups have a significant influence on the morphology of ferrous oxalate dihydrate. However, few studies have provided a theoretical explanation for this effect. In this investigation, the size of ferrous oxalate dihydrate was reduced from micron to nanometer scale using anhydrous ethanol, and its mechanism was elucidated through density functional theory calculations. The calculational results reveal that anhydrous ethanol molecules bound to the ferrous oxalate dihydrate crystal via hydrogen bonding and van der Waals forces, thereby controlling crystal growth. It means that anhydrous ethanol molecules preferentially affected the interlayer interaction in the structure of ferrous oxalate dihydrate, leading to a significant impact on its overall crystal growth way. Furthermore, the electrochemical properties of ferrous oxalate dihydrate synthesized in aqueous and anhydrous ethanol systems were compared and tested. The specific capacitance (242 F ⋅ g−1 at 0.5 A ⋅ g−1 current density) of ferrous oxalate dihydrate synthesized in anhydrous ethanol system is obvious higher than that of ferrous oxalate dihydrate synthesized in water system (186 F ⋅ g−1), due to its smaller particle size (75 nm). Furthermore, the specific capacitance of this material can be improved to 469 F ⋅ g−1 during composite process of ferrous oxalate dihydrate with graphene oxide. In the liquid phase system, ethanol affects the crystallization of ferric oxalate in two ways: first, by adsorbing on the surface structure through hydrogen bonding and van der Waals interactions, and second, by directly adsorbing on the crystal growth direction, refining the grain size. Ethanol preferentially inserts between H2O and C2O42−, altering the internal arrangement of the ferric oxalate crystal structure, thereby influencing the crystal‘s growth direction.